Roos erected the Castles of Helmsley, or Hamlake, in Yorkshire, and of Werke, in Northumberland. He was a member of the Order of Knights Templar. He died in 1226/7 and was buried "in his proper habit" in the Knights' Church, or the New Temple in London, where his tomb may be seen. His effigy is described by Gough, in "Sepulchral Monuments," as "the most elegant of all the figures in the Temple Church, representing a comly young knight in mail, and a flowing mantle with a kind of cowl; his hair neatly curled at the sides; his crown appears shaved. His hands are elevated in a praying posture, and on his left arm is a short, pointed shield charged with three water-bougets. He has on his left side a long sword, and the armor of his legs, which are crossed, has a ridge, or a seam up the front, continued over the knee. At his feet is a lion, and the whole figure measures six feet two inches." He married Isabel, daughter of William the Lion, King of Scotland, and widow of Robert Bruce.